The invention relates to optical scanning devices and more particularly to a portable scanning device for generating a plurality of scanning light beams for scanning a coded label and for collecting the reflected light beams.
In present-day merchandising point-of-sale checkout systems, data pertaining to the purchase of a merchandise item is obtained by reading data encoded indicia such as a bar code label printed on or attached to the purchased merchandise item. In order to standardize the bar codes used in various point-of-sale checkout systems, the grocery industry has adopted a uniform product code (UPC) which is in the form of a bar code. Reading systems which have been constructed to read this type of bar code include stationary optical scanning systems normally located within the cabinet structure of a checkout counter. The bar code is read when a purchased merchandise item is moved across a window in the counter constituting the scanning area of the counter.
Other reading systems employ hand-held laser scanners which emit a single or multiple line scan pattern and which are manually moved past the bar code label that is to be read. It is desirable that handheld laser scanners should provide a high performance scanning operation and have a light weight, compact and balanced hand-held construction. The construction should further provide for ease of movement and reduced hand fatigue in the handling of the scanner and be easily disassembled for testing and for replacement of parts. It is further desirable to have a compact scanner assembly which combines the performance of a stationary scanner with the size, weight, portability, ruggedness and ease of operation of a hand-held scanner.
In order to provide some of these design features, prior bar code scanners or scan generators have utilized a motor-driven hollow drive shaft through which a scanning light beam is projected and then deflected outwardly by a mirror mounted on the end of the shaft. The deflected light beam strikes a plurality of mirrors mounted to deflect the light beam in a forward direction forming a scanning pattern which is moved across a coded label in a reading operation. Examples of this type of bar code scanner construction include U.S. Pat. No. 3,978,317, which discloses an optical reader including a plurality of fixed mirrors disposed on an imaginary circumference, a light source for projecting a light beam through a rotating hollow shaft, a mirror mounted on the end of the hollow shaft for receiving the light beam from the light source and for directing the reflected light beam to the plurality of fixed mirrors successively so as to form a plurality of scanning light beams which are projected on an object, and a photodetector mounted between the rotating mirror and the object for receiving the light beams reflected by the object and for generating an electrical signal in response to receiving the reflected light beams.
In U.S. Pat. No. 4,639,070, there is disclosed a hand-held laser bar code scanning device which includes a basket-shaped array of mirrors which may rotate or be held stationary. Different scan patterns are generated by giving different angles to the mirrors. A rotating hologram is used to generate a conical beam sweep.
In U.S. Pat. No. 4,672,400, there is disclosed a laser scanning device for optically switching an electrostatic printer. The device includes a hollow spindle which is part of the armature of the drive motor. A laser beam is directed through the rotating spindle and folded by an oblique mirror secured to the spindle, to generate a circular sweep. A laser diode may be used as the light source and a focusing lens is fixed within the spindle. The reference discloses the use of directing the beam along the beam axis.
In U.S. Pat. No. 4,699,447, there is disclosed a scanning device for producing a plurality of scan lines including a housing for connection to a beam generator projecting a beam along a beam axis, with a deflecting mirror mounted in the housing obliquely with respect to the beam axis so as to intercept and fold the beam radially outwardly from the beam axis. A plurality of mirrors are disposed outwardly with respect to the beam axis, with each mirror orientated on a tilt angle with respect to the beam axis with the mirrors arranged in a generally basket-shaped array. Each mirror of the basket-shaped array is orientated in such a manner that when it receives a folded beam, it redirects the beam generally in the direction of the beam axis. Rotational drive means are operatively connected to the deflecting mirror or to the basket-shaped array of mirrors for permitting relative rotation of the mirror array and the deflecting mirror about the beam axis. In one embodiment, the basket-shaped array of mirrors is held stationary while the deflecting mirror on the beam axis is rotated. In another embodiment, the basket-shaped array of mirrors is rotated but the deflecting mirror is held stationary. The light beams reflected from the mirrors in the basket-shaped array are directed to form a scan pattern comprising a plurality of scan lines.